This invention relates generally to substrate backings for tapes, and more particularly concerns a tape backing substrate which is flexible, strong, and has the look and feel of cloth.
It is well known in the art to use paper based tapes to secure disposable diapers to infants. Such diaper tapes are subjected to a complex variety of stresses, regardless of the mechanism of these stresses and the failure that may occur to the tape, it is known that such paper based tapes that have a tensile strength of about 11 kg/25 mm and an elongation value of above about 10% (TAPPI Test Method T404-OS-61) have adequate strength for use on diapers. Generally such tape substrates have a basis weight range from 80 to 200 g/m.sup.2 and this is in agreement with Schmidt U.S. Pat. No. 3,797,495.
In the case of this invention, although cellulose fiber is used as in paper based tapes, the combining of unbonded cellulose with rubber-like polymers allows the stress forces to distribute over much larger areas and the tape both in looks and functional characteristics is more like a cloth tape.
Schmidt U.S. Pat. No. 3,797,495 discloses a pressure sensitive adhesive tape for diapers having a substrate consisting of a kraft base with a basis weight of 130 g/m.sup.2 which has been beater treated with nitrile rubber. In another example, the tape substrate has a basis weight of 88 g/m.sup.2 and is made from a bleached kraft fiber saturated with 50 parts per 100 parts of fiber of a combination of 100 parts of a polyacrylate emulsion and one part of an alkylketene dimer sizing agent. While such tapes function adequately for holding diapers on infants, the tapes substrate has the flex and feel of paper.
Desnoyers U.S. Pat. No. 3, 482,683 discloses a pressure sensitive tape consisting of a paper substrate laminated with a film comprising a hypermolecularly oriented linear crystalline polyolefin film. The combination of the crystalline film and paper provide a bundling tape having a relatively low longitudinal extensibility and high resistance to cross-wise tearing forces. The primary strength of the substrate is the oriented film and not the secondary paper layer.
Hienemann et. al. U.S. Pat. No. 3,466,187 discloses a pressure sensitive tape formed from a cellulosic sheet containing 5% to 20% asbestos fibers and impregnated with an elastomeric composition of carboxylated/butadiene/acrylonitrile copolymer latex and coated on at least one side with a pressure sensitive adhesive. Particularly, the nitrile latex used is characterized as a medium hardness latex. The paper substrate contains a major portion of cellulose fiber and is prepared by methods known in the art except for the addition of 5% to 20% by weight of asbestos fibers. In one example, the paper consisted of 10% by weight of asbestos fibers, 80% northern kraft and 10% chemically-curled northern kraft fibers. Such paper substrate has the look and feel of paper.
One of the esthetic drawbacks of conventional disposable diapers is the plastic backing on the diapers which may be objectionable for several reasons. First, esthetically the plastic backing feels uncomfortable when a person is holding an infant who is wearing such a diaper. Second, the plastic film material does not breathe, and therefore, moisture remains trapped inside of the diaper where it can cause diaper rash. With the development of new materials which are impervious to liquid, permeable to air, and have the look and feel of cloth for disposable diapers, it is desirable to have a diaper tape which itself has the look and feel of cloth so that it esthetically compliments the cloth-like materials now being incorporated into new diaper products. In general, the tapes of the prior art that have sufficient strength to perform as diaper tapes, do not have the esthetic qualities of cloth which are desirable.